Pentair 8.50" Triton® II Black Buttress Thread Closure Kit

The Pentair 8.50" Triton® II Black Buttress Thread Closure Kit (part number 154559 or 154559Z) is a specialized, heavy-duty external sealing assembly designed exclusively for the top access dome of Pentair Triton II side-mount sand filtration systems (including models TR40, TR50, TR60, TR100, and TR140) manufactured after 1999. Injection-molded from a thick-walled, high-impact, and UV-stabilized black polymer composite, this comprehensive kit includes the signature 8.5-inch large-diameter dome lid featuring coarse buttress threads, a matching heavy-gauge rubber O-ring, and the manual air relief valve assembly. Its primary structural and operational role is to securely seal the filter's main top-access port, establishing an absolute airtight and watertight pressure boundary capable of safely containing continuous hydraulic flow rates and internal system operating pressures up to 50 PSI without weeping, leaking, or blowing out. Built to endure relentless outdoor UV weathering, intense solar heat, and continuous exposure to concentrated sanitizers like chlorine, bromine, and seasonal acid washes, this robust closure configuration prevents catastrophic pressure loss and allows easy access for media maintenance. Due to its thick-walled, multi-component plastic and rubber architecture designed to span a wide, high-torque opening, the complete closure kit carries a net product and shipping weight of approximately 2.60 to 3.10 pounds (about 41.6 to 49.6 ounces).